This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We are using Quantitative Spectroscopy (QS) to detect dysplasia in the oral cavity in vivo. We have developed the Quantitative Spectroscopy Imaging (QSI) system to collect 121 reflectance and fluorescence spectra in vivo over a 1.1cm x 1.1cm area. Each reflectance spectrum is analyzed using a model of diffuse light propagation to give information about the scattering and absorption properties of the tissue. Each fluorescence spectrum is corrected by the measured reflectance spectrum from the same tissue site to correct for turbidity effects. The resulting intrinsic fluorescence spectra are linearly decomposed to give information about the fluorescence properties of the tissue. Measured scattering, absorption, and fluorescence from each tissue site are used to distinguish high-grade dysplasia from all other tissue conditions. We have two initial clinical targets: 1) identify high-grade dysplasia and invasive cancer amongst oral lesions and 2) identify surgery margins.